REVISITING THE ESTIMATION PROCEDURES IN LIME REQUIREMENT FOR AQUACULTURE POND SOILS

V. Chitra*, R. Saraswathy and M. Muralidhar

ABSTRACT

The accurate estimation of lime requirement for aquaculture ponds to neutralize the acidity of pond bottom soil has been a major concern for many farms. Three methods viz., soil-water pH (1:2.5), soil-buffer pH (Shoemaker-McLean-Pratt buffer) and exchangeable acidity by titration were tested for calculating the lime requirement of four lime materials used by farmers viz., agricultural lime, dolomite, shell lime and sea shell to raise the acidic soil pH from 5.5 to 7. Application rates for lime materials were calculated in terms of pure calcium carbonate with neutralizing value and fineness rating of 100%. Actual lime requirement dose for each lime material was calculated based on effective calcium carbonate equivalent (ECCE) value. The soil was treated with both the calculated and actual dose of lime materials. All the three methods and the dose significantly differed in increasing the soil pH (p < 0.05). Exchangeable acidity method exactly estimates the lime requirement of soil, whereas soil-water pH and SMP buffer methods slightly over and lower estimates the lime requirement respectively. Actual dose of lime material based on ECCE was significant in increasing the pH compared to the calculated dose.

Keywords: Aquaculture acidic pond soils, Soil pH, lime materials